Larry L. Ewing

Follicle-Stimulating Hormone and the Regulation of Testosterone Secretion in Rabbit Testes

Regulation of testosterone secretion is presumably mediated by interstitial cell-stimulating hormone (ICSH). However, there is little information on the actions of other chemical messengers in regulating testosterone secretion. We have shown that follicle-stimulating hormone augments testosterone secretion stimuated by ICSH in rabbit testes perfused in vitro with an artificial medium.

Testicular Metabolism in Adrenalectomized and Corticosterone Treated Rats

Summary Testicular metabolism was examined after adult rats were adrenalectom-ized and/or treated with corticosterone (0.7S, 1.5, and 3.0 mg/day) for 5 days. The weight and DNA and RNA concentrations of testes were not affected by either adrenalectomy or corticosterone replacement but corticosterone (3.0 mg) reduced (p<0.05) testis protein and prevented the loss of testis carbohydrate noted after adrenalectomy. Anaerobic glucose catabolism (cell-free preparations) increased 12% (p<0.05) after adrenalectomy and decreased 13% (p<0.05) after corticosterone (3.0 mg) therapy but neither of these treatments affected aerobic glucose catabolism. Corticosterone (3.0 mg) depressed (p<0.05) the oxidation of glucose-1-14C and glucose-6-14C to 14CO2; whereas adrenalectomy showed a tendency to increase the activity of 14CO2. Testosterone synthesis dropped (p<0.05) after corticosterone (3.0 mg) therapy but was not altered by adrenalectomy. The results suggest that adrenalectomy modifies testicular glucose ca-tabolism and that corticosterone may affect the testis by reducing glucose utilization and testosterone synthesis.

Effect of age upon the spermatogenic and steroidogenic elements of rabbit testes.

Summary Spermatozoa and testosterone production by testes of 6, 12, 24, and 36 month old rabbits were quantified. Testosterone secretion decreased significantly with age when testes were perfused with an artificial medium containing exogenous gonadotropic hormones. Total daily sperm production reached a peak at 24 months and declined significantly by 36 months of age. The fact that sperm production increases through 24 months of age indicates that testosterone secretion is adequate to maintain spermatogenesis. The decreased daily sperm production coincident with reduced testosterone secretion by perfused testes between 24 and 36 months is suggestive of a cause effect relationship.

Comparative metabolic activity of testis and kidney cortex slices of normal and hypoglycemic chickens and rabbits

Abstract 1. 1. Hypoglycemia (produced by insulin injection) for 24 hr caused a decreased respiration of chicken testis but no change in rabbit testis slices. This same treatment caused an increased respiration of chicken and rabbit kidney cortex slices. 2. 2. Oxygen uptake, glucose uptake and lactic acid production of chicken testis slices measured in vitro are higher than those of rabbit testis slices. There was little difference in these criteria between kidney cortex slices from the two species. 3. 3. Homogenate preparations used to measure glycolysis or Krebs cycle activity also showed a significant species difference of testis tissue. 4. 4. The species difference in glycolysis of testis tissue was not due to activity of the enzyme lactic dehydrogenase or to temperature stability of this enzyme.

An enzymatic comparison of glucose metabolism in the rabbit and chicken testis and kidney cortex

Abstract 1. 1. The presence of the glycolytic enzymes were demonstrated in testicular tissue. 2. 2. Chicken tissue predominated in all enzymes in the Embden-Meyerhof pathway with the exception of PK, ‡ whereas rabbit tissue predominated in the various branch-points of glycolysis (G-6-P DH, 6-PG DH, PGM, α-Gly-P DH). 3. 3. Kidney cortex, regardless of species, was significantly higher in all enzyme activities except hexokinase, G-6-P DH, and PK in which testis was significantly higher. 4. 4. Three of the enzymes (hexokinase, G-6-P DH, and PK) demonstrated a significantly higher difference in the activity of the testis as compared to that of kidney cortex. 5. 5. From the above data and previous observations, a hypothesis was constructed in an attempt to explain the difference in metabolism of the abdominal testis (chicken) and the scrotal testis (rabbit).